This invention relates generally to a temperature adjusting system for adjusting temperature of a predetermined space by controlling temperature of a medium such as a gas, fluid or solid, for example. More particularly, the invention concerns a non-interference type temperature adjusting control system, and an exposure apparatus having such a control system.
An apparatus for reducing a circuit pattern formed on an original, such as a reticle through a projection optical system and for transferring the same to a substrate such as a semiconductor wafer, is called a semiconductor exposure apparatus. Usually, it is called a stepper. Recently, a semiconductor exposure apparatus in which an exposure process is carried out by moving a reticle stage carrying thereon a reticle and a wafer stage carrying thereon a semiconductor wafer, in opposite directions in synchronism with each other, and at a predetermined speed ratio, has been developed, and it is called a scanner. In such semiconductor exposure apparatuses, the apparatus structure as a whole is accommodated in a temperature controlled chamber.
In recent years, in order to meet requirements for improved productivity of an exposure apparatus, such as a semiconductor exposure apparatus, positioning mechanisms such as an original stage (e.g., a reticle stage) and a substrate stage (e.g., a wafer stage), for example, are made to be driven at higher speeds. This causes increased heat generation in actuators for driving these stages. It disturbs the light path of an interferometer used for the positioning of the stage and, consequently, it results in deterioration of the positioning precision. Further, since heat generation causes expansion/contraction in size of various structural components, this deteriorates the measurement precision. For these reasons, improvements in precision of temperature control for a chamber for accommodating an exposure apparatus have been desired.
Conventionally, in order to keep a predetermined temperature inside a chamber, a gas is once cooled and then it is re-heated by using a temperature adjuster. After a desired temperature is reached, the gas is supplied into a space where a constant temperature is to be maintained. Here, the gas may be air, nitrogen gas, or helium, for example. Now, air is taken as an example of an operative gas. However, the following description applies to nitrogen gas or helium as an operative gas.
First, referring to FIG. 14, a conventional temperature control system will be explained. FIG. 14 shows a structure of a temperature control system of a known type, wherein denoted at 501 is an air blower for discharging air cooled by a cooling unit (not shown), and denoted at 502 is a re-heating heater for re-heating the air supplied from the blower 501. Denoted at 503 is a duct for introducing the re-heated air, and denoted at 504 is temperature measuring means for measuring the temperature at an air blowing outlet port. Denoted at 505 is temperature controlled air, and denoted at 506 is a temperature controlled space, which depicts an approximate space where the temperature is going to be controlled. This space 506 accommodates therein a stage 507 as a positioning mechanism of a semiconductor exposure apparatus, and a laser interferometer 508 as position measuring means for positioning control of the stage 507.
In the temperature controlled space 506, since the stage 507 is driven with acceleration and deceleration at high speeds, heat is generated by actuators, not shown. This causes deviation of the temperature inside the space 506 from a predetermined value. The temperature measuring means 504 measures the temperature of the air at the air blow outlet port, and an output thereof is applied to a temperature controller 509 whereby an appropriate compensation signal is produced. This compensation signal is applied as an input to a driver 510 for controlling the amount of voltage application to the re-heating heater 502, such that the voltage application to the heater 502 is controlled and, thus, the heating amount to the cool air supplied from the blower 501 is controlled. As a result, air being controlled to a constant temperature can be supplied into the space 506 from the air blow outlet port. The temperature controller 509 can be used for temperature control in a plant, for example, and it has a function for mainly accomplishing PID compensation wherein, as well known in the art, P means proportion, I means integration and D means differentiation.
The temperature controlling system shown in FIG. 14 is based on such a concept that temperature controlled air 505 should be produced and the space 506 should be filled with the same. There is a heat generating source inside the space 506 as an external disturbance factor, and it may cause deviation of the temperature inside the space 506 from a desired temperature. Since, however, the temperature measuring means 504 is hidden inside the duct 503 rather than being exposed in the space 506, the temperature measuring means 504 does not sense a temperature change inside the space 506 immediately. Namely, in this system, air 505 having been controlled at a designated temperature is consistently supplied into the temperature-deviated space 506, thereby to correct the deviated temperature. In other words, the space 506 is controlled at a designated temperature by substituting the air inside the space 506, having a temperature deviated from a desired temperature, by air having been temperature controlled and kept at a designated temperature. Thus, it should be noted that in the structure of FIG. 14 the space 506 is not directly temperature controlled. Any external disturbance produced inside the space 506 is never directly detected, and it means that the function for suppressing a temperature change due to external disturbance is very poor. For this very reason, conventionally, an additional mechanical structure, such as a shield for encircling the space 506, is used to prevent external disturbance from entering the space 506.
For better understanding of the above, an analogy is introduced here. FIG. 15 shows a mechanical system in which, by driving a motor 511, an inertial load 513 connected thereto through a spring 512 is rotationally driven. This mechanical system is functionally equivalent to the temperature control system described above.
In FIG. 15, the motor 511 is controlled on the basis of an output of a sensor 514. More specifically, in terms of a rotational speed or rotational displacement, the state of the motor 511 is detected, and the detection result is fed back to a controller 515. Thus, while the motor shaft may be controlled accurately, the inertial load 513 connected to the motor through the spring 512 is left uncontrolled. Therefore, even if a torque external disturbance 516 is applied to the inertial load 513 and the rotational speed or rotational displacement of the inertial load 513 changes, it is possible that the rotational speed or rotational displacement at the motor 511 side is unchanged.
The temperature controlling structure shown in FIG. 14 can be regarded as being an equivalent to this. Specifically, the state detection at the motor 511 side by the sensor 514 corresponds to the temperature detection at the air blow outlet port by the temperature measuring means 504, and the torque external disturbance applied to the inertial load 513 corresponds to the external disturbance entering the space 506. Therefore, as in the case of FIG. 15, wherein the rotational speed or displacement of the inertial load 513 may change relative to the motor 511 shaft in response to the torque external disturbance applied to the inertial load 513, it is clear in FIG. 14 that, when external disturbance influences the space 506, the temperature in the space changes relative to the air temperature as controlled at the location of the temperature measuring means 504. Although the temperature of the air at the air blow outlet port of the duct 503 is controlled in this system, what is to be the duly controlled constant is the temperature inside the space after the air blow outlet port. Yet, there are various external disturbances, which may cause deviation of the set temperature. Nevertheless, in the conventional temperature controlling system, the temperature of the space 506, which is inherently to be temperature-controlled, is not measured. Quite naturally, the temperature of the space 506, itself, is not controlled positively.
If the temperature of the space 506 is measured and it is fed back to control the re-heating heater 502, the temperature control of the space 506 may be complete. Practically, however, feedback stabilization and temperature controller 509 tuning to ensure satisfactory suppression of external disturbances are absolutely difficult to accomplish. This is because of the following reasons. Comparing the distance from the re-heating heater 502 to some temperature measuring means to be provided inside the space 506 with the distance from the same re-heating heater 502 to the temperature measuring means 504 disposed adjacent to the air blow outlet port, clearly the former is longer and, thus, dead time is inevitably longer in the former, causing the temperature controllability to worsen. Further, since the temperature of the space 506 fluctuates due to the influence of external disturbances, it is readily understood that stabilization of a closed loop system based on feedback of varying measured values is not easy. For these reasons, conventionally, temperature measurement has to be carried out at a position not directly influenced by external disturbance, for example, the air blow outlet port covered by the duct 503, and, by feeding back the measured value, temperature control is performed.
However, what is to be just controlled to be constant is the very temperature of the space 506 being exposed to external disturbances. In order to meet requirements for further device miniaturization and improved productivity of a semiconductor exposure apparatus, a temperature control system capable of directly controlling the temperature of a space, such as the temperature controlled space 506, has been desired.
FIG. 16 is a schematic view for explaining a conventional air conditioning unit. Denoted in the drawing at 21 is a thermostatic chamber, and denoted at 22 is an exposure apparatus disposed inside the chamber 21. Denoted at 23 is a booth. Adjacent to the booth 23, there is an air conditioning passageway 24 for supplying a gas of a predetermined set temperature. From this air conditioning passageway 24 and through a filter 25, a gas is blown into the booth 23 to thereby keep the booth 23 clean and at a constant temperature. Disposed along the air conditioning passageway 24 is an air conditioning unit 29, which includes a heat exchanger 26, a blower 27 and a re-heater 28. Also, there are an external air introducing inlet port 30 for introducing external air, a communication port 31 being communicated with the booth 23, and a gas discharging outlet port 32 for discharging the gas inside the booth 23 outwardly.
Major components placed in the booth 23 will now be explained. In the following description, the words xe2x80x9cair conditioningxe2x80x9d and xe2x80x9ctemperature controllingxe2x80x9d or xe2x80x9ctemperature adjustingxe2x80x9d will be used equivalently. First, light emitted from a light source (not shown) is projected on a reticle 33 having a circuit pattern for production of semiconductor devices. Light passed through the reticle goes through a projection optical system 34 and, while being reduced to ⅕ or xc2xc thereby, it is projected onto a semiconductor wafer 35. The wafer 35 is placed on a wafer stage (X-Y stage) 36. The wafer stage 36 is mounted on an anti-vibration table 37. Denoted at 38 are active mounts, constituting an active anti-vibration system. The function of this unit is to suppress vibration of the major assembly structure including the anti-vibration table 37, to be produced by drive reaction forces resulting from step-and-repeat motion or high-speed scan motion of the wafer stage, accompanied by sudden acceleration and deceleration. Also, it has a function to prevent vibration of the floor on which the exposure apparatus 22 is placed, from being transmitted to the major assembly structure including the projection optical system 34.
As regards the temperature inside the booth 23, temperature measuring means 39a detects a temperature near the exit of the filter 25. The detection output thereof is applied to a controller 40. In most cases, the controller 40 performs a PID compensation operation to a differential signal, which is produced by comparing a target temperature set in the controller 40 and the result of measurement by the temperature measuring means 39a. The compensation output is applied as an input to a re-heater 28 (hereinafter, xe2x80x9ctemperature converting meansxe2x80x9d), including a re-heating heater 2 and a driver (e.g., solid state relay SSR) for supplying an electric voltage to the heater. In response, the voltage application to the heater 2 is adjusted so that the temperature becomes equal to the target temperature set in the controller 40. What is described above with reference to FIG. 16 is a general structure of an air circulation passageway and a temperature control system, for controlling the booth 23 approximately to be at a constant temperature.
Practically, in addition to the temperature control on the basis of an output of the temperature measuring means 39a, separate air conditioning means is provided independently. For example, in relation to the spaces related to the projection optical system 34, the wafer stage 36, and a reticle stage (not shown) for positioning the reticle 33, and so on, respectively, temperature control is carried out locally and concentratedly to these spaces. In most cases, the temperature control is carried out by supplying a gas being controlled at a constant temperature into each space. Only an output of temperature measuring means provided at the air blow outlet port is fed back. This type of temperature control will hereinafter be referred to as xe2x80x9cblower outlet controlxe2x80x9d.
However, the space just to be controlled at a constant temperature is after the blowing outlet port, and external disturbances are present there. What can be called xe2x80x9cuse point control,xe2x80x9d which is based on temperature measurement to a space just to be temperature controlled, has never been carried out.
Now, a performance comparison will be made to the blower outlet control and the use point control. FIGS. 17A-17C show results of measurements actually made to the blower outlet control, wherein FIG. 17A shows the use point temperature (it is only monitored), FIG. 17B shows the blowing outlet port temperature, and FIG. 17C shows the temperature of an external disturbance source. In response to application of an external disturbance, such as shown in FIG. 17C, the blowing outlet port temperature changes for a moment. However, in this structure, basically, the temperature measuring means provided at the blowing outlet port does not sense a temperature change at a use point. Therefore, after a flash change at the moment of external disturbance application, it continues the supply of air at the designated temperature. Yet, the temperature at the use point is left deviated due to the external disturbance, as long as it is within the time span as illustrated in the drawing.
On the other hand, FIGS. 18A-18C show the results of measurements actually made to the use point control, wherein temperatures shown in FIGS. 18A-18C correspond to the temperatures of FIGS. 17A-17C, respectively. In this case, in response to external disturbance application, such as shown in FIG. 18C, the temperature of the gas from the blowing outlet port (FIG. 18B) changes. It is seen that, by supplying temperature-changed gases from the blowing outlet port, the influence of the external disturbance is cancelled and, as shown in FIG. 18A, the temperature at the use point is turned quickly back to the designated temperature.
It is seen that, with the use point temperature control, as compared with blower outlet control, the temperature of the space, which is just to be temperature controlled, can be controlled at a high precision. At least when the exposure apparatus is in a normal operation state and the thermostatic chamber is steadily operated, clearly, the use point control is superior.
However, for example, if the gas-tightness of the thermostatic chamber of an exposure apparatus is interrupted by opening a door of the chamber, continuous operation of the use point control will cause a malfunction and, in a worst case, stoppage of the thermostatic chamber operation. The reason is that, as compared with the temperature control for a closed space (as a thermostatic chamber), a temperature change to be applied from outside of the chamber is continuous and overwhelming, and it goes beyond the capacity of the temperature converting means for conditioning the chamber. While it depends on the level of changed temperature, it is possible that the temperature converting means continuously produces a null output or maximum output. Also, if a limiter is set for the output of the temperature converting means, the output may be fixed to the upper or lower limit thereof.
In the case of blower output control, on the other hand, if the door of the thermostatic chamber is opened, the temperature adjacent to the use point may be disturbed, whereas the temperature at the blowing outlet port may not be disturbed. Thus, even if the temperature around the use point goes away from the designated temperature to cause a substantial error, adversely affecting the exposure performance, the temperature control with regard to the blowing outlet port can be continued as if there is no change by the external disturbance. In other words, without causing abnormal heating of the temperature converting means, for example, or without causing stoppage of the thermostatic chamber, the operation can be kept stable. Then, if the door of the thermostatic chamber is closed, since the gas from the blowing outlet port is at a constant temperature, after an elapse of quite a long time, the temperature at the use point also turns back to the predetermined temperature.
In the structure of FIG. 16, in connection with the spaces related to the projection optical system 34, the wafer stage 36, and a reticle stage (not shown) for positioning the reticle 33, respectively, temperature control is carried out locally and concentratedly to each of them. The exposure apparatus 22 operates while operating these local air conditioning systems in parallel.
Conventionally, such local air conditioning systems in an aggregation are operated in parallel to each other. A large technical problem is involved in this respect. Idealistically, local air conditioning systems should operate as mutually independent systems, without affecting each other. Practically, however, the local air conditioning systems interfere with each other. For example, adjustment made to improve a certain local air conditioning system may act as an external disturbance to another local air conditioning system. It is, therefore, difficult to improve the temperature controllability of the thermostatic chamber, as a whole.
Japanese Laid-Open Patent Application No. 2000-187514 proposes a structure for avoiding such interference in a temperature control system. FIG. 19 shows a non-interference temperature control system with a dual-input and dual-output temperature adjuster, based on this proposal.
Denoted in the drawing at 517 is a temperature adjusting system, which comprises first and second heaters 518A and 518B (temperature converting means), and first and second temperature sensors 519A and 519B (temperature measuring means).
The outputs of the first and second temperature sensors 519A and 519B are applied to average temperature and gradient temperature calculating means 520 (hereinafter, xe2x80x9cmode temperature calculating meansxe2x80x9d), in which an average temperature and a gradient temperature are calculated on the basis of the outputs of the sensors 519A and 519B. The average temperature and the gradient temperature are compared with values applied to target value input terminals 521A and 521B, respectively, whereby deviation signals err1 and err2 are produced. These signals are applied to first PID control means 522A and second PID control means 522B, respectively, whereby a control input is calculated.
The outputs of the first and second PID control means 522A and 522B are applied to distributing means 523, by which control inputs to be produced by the first and second heaters 518A and 518B, disposed spatially separately, are determined.
Viewing it in perspective, the system structure of FIG. 19 can be regarded as being a control system for mode control. For example, in the field of machine control, a control loop structure based on a kinetic mode for translation and rotation will be similar to such as shown in FIG. 19. This is not limited to the kinetic mode. A control loop structure based on a vibration mode for individually defining a vibration mode of a mechanical system (controlled subject) is quite similar to that of FIG. 19. The FIG. 19 structure is notable in that it introduced the concept of kinetic modes or vibration modes peculiar to the position or vibration control of a mechanical system, into the field of temperature control. The interference between local temperature control systems may apparently be reduced with this structure. However, there still remain problems to be solved.
First of all, in the structure such as proposed in Japanese Laid-Open Patent Application No. 2000-187514, there is an implicit prerequisite condition that controlled systems to be temperature controlled must have substantially the same dynamic characteristics.
This will be explained in detail in conjunction with a case wherein the temperature control system for the controlled subject comprises dual-input and dual-output systems such as shown in FIG. 19. The transfer function matrix can be expressed as shown in FIG. 20. Here, how the elements of the transfer function matrix take a specific form differs in dependence upon what the temperature control system is just going to temperature-control. For example, when temperature control is to be carried out to an object having a uniform thickness by use of heaters disposed at two locations and on the basis of outputs of two temperature measuring means provided adjacent to the heaters, it can be expressed as follows.
G11(s)=G22(s)=[Kp/(1+Tp(s))]exp(xe2x88x92Lp1(s))xe2x80x83xe2x80x83(1)
Namely, transfer functions of diagonal elements are about the same. Of course, non-diagonal terms are proportional. Japanese Laid-Open Patent Application No. 2000-187514 supposes use of controlled systems as described above. Here, symbols used in equation (1) above can be readily understood by those skilled in the art. Therefore, a detailed description thereof will be omitted.
In the dual-input and dual-output system, if the parameters of G11(s) and G22(s) differ largely, it may be expressed by equations (2) and (3) below.
xe2x80x83G11(s)=[Kp1/(1+Tp1s)]exp(xe2x88x92Lp1s)xe2x80x83xe2x80x83(2)
G22(s)=[Kp2/(1+Tp2s)]exp(xe2x88x92Lp2s)xe2x80x83xe2x80x83(3)
Of course, Kp1xe2x89xa0Kp2, Tp1xe2x89xa0Tp2 and Lp1xe2x89xa0Lp2. Namely, while the form of the transfer function itself is the same, values of the parameters differ largely, such that the responsibility differs. Alternatively, there may be a plant that can be expressed by equations (4) and (5) as follows.
G11(s)=[Kp1/(1+Tp1s)]exp(xe2x88x92Lp1s)xe2x80x83xe2x80x83(4)
G22(s)=[Kp2/{(1+Tp2s)(1+Txe2x80x2p2s)}]exp(xe2x88x92Lp2s)xe2x80x83xe2x80x83(5)
In this case, there is an essential difference in dynamics between G11(s) and G22(s), and there is a large difference in responsibility. Of course, in the cases of equations (2) to (5), elements 12 and 21 become interference terms, and, anyway, they treat an interference system in which a transfer function is present.
The air conditioning system in an exposure apparatus is a system that can be expressed by equations other than equation (1), that is, by equations (2) and (3) or, alternatively, by equations (4) and (5).
For example, the time constant of a system for controlling the whole space inside a thermostatic chamber at a constant temperature would be large. On the other hand, a system which is operated in parallel with the temperature control of a large space (as a thermostatic chamber) to perform local air conditioning only to a limited space of a stage, would be small in time constant and short in dead time. Namely, it is a quick response system. Of course, unless these parameters are small, there is no meaning of providing a local air conditioning system to a stage space, which is a very important space in relation to the exposure performance. As compared with the temperature control system for the thermostatic chamber space, this system accomplished higher responsibility of a re-heating heater, higher speed of blower means, and higher speed of temperature measuring means, thereby to assure quick responsibility. Anyway, the presence of disturbance in temperature control of the thermostatic chamber space leads to fluctuation in temperature of the stage space, and vice versa. Namely, the system is a mutually interfering system.
Even if the matrix elements of the mode temperature calculating means 520 and the distributing means 523 shown in FIG. 19 are incorporated as constant coefficients to a system in which the dynamics differ largely, such as described above, due to a large difference in dynamics involved, the non-interference system would not operate well.
Japanese Laid-Open Patent Application No. 2000-187514 refers to something other than matrix elements as constant coefficients. In fact, there is a statement xe2x80x9cAlthough in this embodiment the distribution ratio (non-interference coefficient) is calculated by use of a transfer coefficient, as another embodiment, in place of the transfer coefficient, a transfer function, which represents the frequency characteristic may be used to calculate the same.xe2x80x9d This is a clear statement that the elements of the matrix operation are not limited to the constant coefficient. In other words, it means that the content of the distributing means can be determined while taking the dynamics of a controlled subject into consideration.
This operation may correspond to obtaining an inverse system, for example. However, it cannot be applied to a controlled subject including a dead time, such as a temperature control system. For, the inverse system of equation (1) can be expressed by the following equation.
G11(s)xe2x88x921=[(1+Tps)/Kp]exp(Lps)xe2x80x83xe2x80x83(6)
Here, a state being not proper (problem of order) can be solved by insertion of a filter, which is effective to increase the order of the fraction. However, in the inverse system G11xe2x88x921, the dead time in G11(s) must function as a prediction time Lp, and this is impossible. This will be readily understood from that, since an unstable null point emerges in the numerator of a transfer function where the dead time is Hardy approximated, this null point becomes an unstable pole in the transfer function of the inverse system.
Alternatively, it may be contemplated that a physically attainable transfer function is incorporated as elements of the distributing means 523. However, an algorithm or a searching method for calculating such a transfer function has never been known. For theses reasons, it is practically impossible to incorporate elements having frequency characteristics to the elements of the distributing means 523.
The background of the present invention can be summarized as follows.
In the field of precise temperature control, conventionally, circulation air is once cooled and, thereafter, it is re-heated under temperature control. The re-heated air is fed into a space (temperature controlled space) where the temperature control is just to be done. The amount of re-heating the air depends on feedback control, which is based on an output of temperature measuring means. However, the temperature measuring means is not disposed in the space in which the temperature control should be done. In accordance with the concept that air of a desired temperature should be produced by a re-heating heater and it should be fed into the temperature control space, the temperature control of a chamber in an exposure apparatus, such as semiconductor exposure apparatus, has been carried out.
To the contrary, a temperature controlled space in an exposure apparatus is an environment attributable to the exposure performance and, therefore, any influence of an external disturbance should be reduced immediately. Nevertheless, feedback control based on a detected temperature of the temperature control space has never been carried out. This is because the dead time depending on the distance, for example, from the re-heating heater to the temperature measuring means will become longer and, therefore, stabilization of the control loop will become difficult to achieve. Further, the external disturbance in the temperature control space will be detected with high sensitivity, and this will make the control loop settlement worse.
Further, in conventional temperature control systems for a thermostatic chamber in an exposure apparatus, a gas being controlled at a constant temperature is supplied from a blowing outlet port. Temperature measuring means is provided adjacent to the blowing outlet port, and the output thereof is fed back.
However, with such blowing outlet port temperature control, it is impossible to turn back the temperature of the space (to be controlled constant) promptly, under an external disturbance state. There is a concept of use point control in which, in addition to the blower outlet port, the temperature of a space just to be controlled at a constant temperature is detected and it is fed back. As compared with the blower outlet control, this method has a potential of turning back the temperature to a designated temperature promptly, against an external disturbance applied to the controlled space.
The actual operation of a thermostatic chamber of an exposure apparatus has to accept a large external disturbance, disturbing the temperature stability, such as by opening a door. With conventional blower outlet control, a change in external disturbance is not detected, and the supply of constant-temperature gas from the blowing outlet port continues. Therefore, the temperature control system operates continuously as usual. In the use point control, however, due to the application of a large external disturbance as by opening the door, it is possible that the temperature converting means continuously outputs a maximum value, for example. On such an occasion, the feedback system malfunctions and, in a worst case, the operation of thermostatic chamber stops. The stoppage of the chamber is a large obstruction to the continuous operation of the exposure apparatus and, therefore, it must be avoided. Further, in addition to avoiding the chamber stoppage, turning the chamber space back to a desired temperature promptly has been desired.
Further, in a thermostatic chamber of an exposure apparatus, the air conditioning process is carried out by use of a medium (in many cases, gas) of constant temperature. Specifically, a plurality of local air conditioning systems are operated in parallel to each other, to accomplish temperature control to a space directly concerning the exposure performance of the exposure apparatus as well as peripheral spaces communicated with that space. However, theses local air conditioning systems interfere with each other (interference system) and, because of such an interference feature, adjustment to improve the performance of the temperature control system as a whole is difficult to attain.
In order to avoid such an interference feature, Japanese Laid-Open Patent Application No. 2000-187514 proposes a non-interference system having superior controllability. However, in order to actually apply the proposed temperature control system to an exposure apparatus, there still remain large problems. Namely, in fact, there is a limitation that the controlled subjects to be treated by the proposed method should have substantially the same dynamics. As a result of this, it is practically impossible to insert a constant coefficient matrix operation into the feedback loop to avoid the interference feature.
Generally, temperature control systems operated in an exposure apparatus have inherently slow dynamics and yet they differ from each other. Thus, even if the proposed concept is applied simply to a temperature control system in an exposure apparatus, expected results would not be attainable. Moreover, since their dynamics differ from each other, prevention of interference itself may not function well.
It is accordingly an object of the present invention to provide a temperature adjusting system by which the precision of temperature control for a space where the temperature control is to be done can be improved, and also to provide an exposure apparatus having such a temperature adjusting system which can meet the requirements of improvements in precision and productivity of the exposure apparatus.
It is another object of the present invention to provide a temperature adjusting system to be operated in an exposure apparatus and having a function for switching a control loop structure in accordance with gas-tightness of a thermostatic chamber, for example, and also to provide an exposure apparatus having such a temperature adjusting system.
It is a further object of the present invention to provide a non-interference type temperature adjusting control system to be operated in an exposure apparatus and having plural local air conditioning systems operable in parallel to each other, by which high-speed response is accomplished and mutual interference is avoided or reduced, and also to provide an exposure apparatus having such a non-interference type temperature adjusting control system.
In accordance with an aspect of the present invention, there is provided a temperature adjusting system, comprising: a blowing outlet port for supplying a medium into a subject to be temperature controlled; first temperature measuring means for measuring a temperature at said blowing outlet port; a first temperature controller for performing a compensation operation in response to an output of said first temperature measuring means; second temperature measuring means for measuring a temperature of a temperature control space, which is downstream of said blowing outlet port; a second temperature controller for performing a compensation operation in response to an output of said second temperature measuring means; and temperature converting means for controlling an amount of heat generation on the basis of an output of said first temperature controller so that a medium being controlled at a constant temperature is supplied into said temperature control space from said blowing outlet port, wherein a predetermined temperature set value corresponding to a desired value for the temperature for the temperature control space is inputted to said second temperature controller, and wherein an output of said second temperature controller is inputted to said first temperature controller as a temperature set value for said first temperature controller.
In one preferred form of this aspect of the present invention, said first temperature controller is arranged to re-heat a medium once cooled and to supply a medium controlled at a constant temperature into said temperature control space.
A plurality of second temperature measuring means each being as aforesaid may be disposed in a distribution with respect to the temperature controlled subject, wherein said temperature adjusting means may further comprise operation means for calculating one of a simple average or a weighted average of a temperature measured value from outputs from said plurality of second temperature measuring means, and wherein an output of said operation means may be applied to said second temperature controller as negative feedback.
The temperature controlled subject may be at least one of a stage space in an exposure apparatus, a projection optical system and a booth for accommodating the exposure apparatus therein.
The first temperature controller may be based on a PID control method, while said second temperature controller may be based on a difference differential PID control method.
The temperature adjusting system may further comprise discriminating means for monitoring a stage in a temperature controlled thermostatic chamber and for discriminating the state inside said chamber on the basis of the monitoring, and switching means for changing an input of said first temperature controller between an output of said second temperature controller and the predetermined target value to said first temperature controller, on the basis of an output of said discriminating means.
The first temperature controller may be arranged to perform a PID operation while said second temperature controller may be arranged to perform a PI operation.
In accordance with another aspect of the present invention, there is provided a temperature adjusting system, comprising: a blowing outlet port for supplying a medium into a subject to be temperature controlled; first temperature measuring means for measuring a temperature adjacent to said blowing outlet port; a first temperature controller for performing negative feedback of an output of said first temperature measuring means; second temperature measuring means for measuring a temperature of a temperature control space, which is downstream of said blowing outlet port; a second temperature controller for performing negative feedback of an output of said second temperature measuring means; and temperature converting means for controlling an amount of heat generation on the basis of an output of said first temperature controller so that a medium being controlled at a constant temperature is supplied into said temperature control space from said blowing outlet port, wherein a predetermined temperature set value corresponding to a desired value for the temperature for said temperature control space is inputted to said second temperature controller, and wherein an output of said second temperature controller is inputted as a temperature set value for said first temperature controller.
In accordance with a further aspect of the present invention, there is provided a non-interference type temperature adjusting control system, comprising: temperature converting means for variably changing a temperature of a medium to be supplied into a controlled subject; a plurality of first temperature measuring means for measuring the temperature of the medium adjusted by said temperature converting means; a plurality of second temperature measuring means for measuring a temperature of the controlled subject; a minor loop system including a feedback system for actuating said temperature converting means on the basis of outputs of said first temperature measuring means; mode temperature calculating means for calculating an average temperature and a gradient temperature of the controlled subject on the basis of outputs of said first temperature measuring means; and distributing means for producing an output to said minor loop system in response to a signal obtainable by compensation to an output of said mode temperature calculating means.
In one preferred form of this aspect of the present invention, said minor loop system includes PID control means for determining a control input to said temperature converting means in response to an output of said second temperature measuring means and to a signal obtainable by performing compensation to an output of said mode temperature calculating means, and wherein said PID control means includes adjusting means for adjusting a response up to said first temperature measuring means in said minor loop system.
In accordance with a yet further aspect of the present invention, there is provided an exposure apparatus, comprising: transferring means for transferring a pattern of an original onto a substrate; and a temperature adjusting system including (i) a blowing outlet port for supplying a medium into a subject to be temperature controlled, (ii) first temperature measuring means for measuring a temperature at said blowing outlet port, (iii) a first temperature controller for performing a compensation operation in response to an output of said first temperature measuring means, (iv) second temperature measuring means for measuring a temperature of a temperature control space, which is downstream of said blowing outlet port, (v) a second temperature controller for performing a compensation operation in response to an output of said second temperature measuring means, and (vi) temperature converting means for controlling an amount of heat generation on the basis of an output of said first temperature controller so that a medium being controlled at a constant temperature is supplied into said temperature control space from said blowing outlet port, wherein a predetermined temperature set value corresponding to a desired value for the temperature for said temperature control space is inputted to said second temperature controller, and wherein an output of said second temperature controller is inputted to said first temperature controller as a temperature set value for said first temperature controller.
In accordance with a still further aspect of the present invention, there is provided an exposure apparatus, comprising: transferring means for transferring a pattern of an original onto a substrate; and a non-interference type temperature adjusting control system including (i) temperature converting means for variably changing a temperature of a medium to be supplied into a controlled subject, (ii) a plurality of first temperature measuring means for measuring the temperature of the medium adjusted by said temperature converting means, (iii) a plurality of second temperature measuring means for measuring a temperature of the controlled subject, (iv) a minor loop system including a feedback system for actuating said temperature converting means on the basis of outputs of said first temperature measuring means, (v) mode temperature calculating means for calculating an average temperature and a gradient temperature of the controlled subject on the basis of outputs of said first temperature measuring means, and (vi) distributing means for producing an output to said minor loop system in response to a signal obtainable by compensation to an output of said mode temperature calculating means.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.